1. Field of the Invention
The present invention relates to internal combustion engines and, more particularly to a transfer system.
2. Background Art
U.S. Pat. No. 6,367,432 discloses a two-stroke cycle internal combustion engine which has a quaternary Schnurle-type scavenging system that is configured such that the capacity of a pair of second scavenging passageways are made larger than te capacity of a pair of first scavenging passageways, so that during the descending stroke of the piston, air is allowed to be introduced into the combustion actuation chamber from the second scavenging passageways prior to the introduction of the air-fuel mixture and at the same time, a relatively large quantity of air is allowed to be introduced into the combustion actuating chamber from the first scavenging passageways over a longer period of time as compared with the period of time in which air is introduced from the second scavenging passageways.
U.S. Pat. No. 6,223,705 discloses a two-stroke internal combustion engine having a Schnurle scavenging system includes a pair of first scavenging ports and a pair of second scavenging ports. An inner horizontal scavenging angle formed close to an exhaust port and an outer horizontal scavenging angle formed remote from the exhaust port by a pair of scavenging flows blown out of the pair of the first scavenging ports are both set to an angle in the range of from 116 to 124 degrees. An inner horizontal scavenging angle formed close to the exhaust port and an outer horizontal scavenging angle formed remote from the exhaust port by a pair of scavenging flows blown out of the pair of the second scavenging ports are set to angles in the ranges of rom 126 to 135 degrees and from 146 to 154 degrees, respectively.
Because of increasing government pollution emissions standards, there is a continuing need to lower engine emissions in two-stroke engines. One of the sources of emission problems has been the discharge of unburned hydrocarbons due to short circuiting of fuel out of an exhaust port during an upward stroke of the piston before the exhaust port is closed. Thus, there is a need to minimize the loss of fresh, short circuit fuel exiting out of the exhaust. This minimization can result in lower hydrocarbon emissions and higher fuel economy.